A rubber composition

ABSTRACT

A rubber composition is based on at least an elastomer matrix comprising at least one first diene elastomer bearing at least one SiOR1 function, R1 being a hydrogen atom or a hydrocarbon radical, the SiOR1 function not located at the chain ends of the first diene elastomer, a reinforcing filler comprising a reinforcing inorganic filler, and a plasticizing agent comprising a liquid plasticizer comprising a liquid diene polymer bearing at least one function.

TECHNICAL FIELD

The field of the invention is rubber compositions, for example, for arubber article, particularly for tires, shoes or caterpillar tracks,more particularly for tires, still more particularly for tire treads.

BACKGROUND ART

In a known way (for example, the following patent literature 1), liquiddiene polymers have been used in rubber compositions of rubber articlesin order to improve the processability.

CITATION LIST Patent Literature

PTL 1

EP1035164

However, the improvement by the liquid diene polymer can bedisadvantageous to the hysteresis property of the rubber compositions,and thus a constant objective of the manufactures of the articles isimprovement of balance of performances (the processability and thehysteresis property).

SUMMARY OF INVENTION Technical Problem

During the research, the inventor has discovered a specific rubbercomposition which allows an unexpectedly improved balance ofperformances between the processability and the hysteresis property.

In the present description, unless expressly stated otherwise, all thepercentages (%) indicated are percentages by weight (wt %).

The expression “elastomer matrix” is understood to mean, in a givencomposition, all of the elastomers present in said rubber composition.

The abbreviation “phr” signifies parts by weight per hundred parts byweight of the elastomer matrix in the considered rubber composition.

In the present description, unless expressly indicated otherwise, eachTg_(DSC) (glass transition temperature) is measured in a known way byDSC (Differential Scanning calorimetry) according to Standard ASTMD3418-08.

Any interval of values denoted by the expression “between a and b”represents the range of values of more than “a” and of less than “b”(i.e. the limits a and b excluded) whereas any interval of valuesdenoted by the expression “from a to b” means the range of values goingfrom “a” to “b” (i.e. including the strict limits a and b).

The expression “based on” should be understood in the presentapplication to mean a composition comprising the mixture(s) and/or theproduct of the reaction of the various constituents used, some of theconstituents being able or intended to react together, at least partly,during the various manufacturing phases of the composition, inparticular during the vulcanization (curing).

Solution to Problem

A first aspect of the invention is a rubber composition based on atleast an elastomer matrix comprising at least one first diene elastomerbearing at least one SiOR₁ function, R₁ being a hydrogen atom or ahydrocarbon radical, the SiOR₁ function not located at the chain ends ofthe first diene elastomer a reinforcing filler comprising a reinforcinginorganic filler, and a plasticizing agent comprising a liquidplasticizer comprising a liquid diene polymer bearing at least onefunction.

Advantageous Effects of Invention

The specific rubber composition allows improving the balance ofperformances between the processability and the hysteresis property.

Each of the below aspect(s), the embodiment(s) and the variant(s)including each of the preferred range(s) and/or matter(s) may be appliedto any one of the other aspect(s), the other embodiment(s) and the othervariant(s) of the invention unless expressly stated otherwise.

Elastomer (or loosely “rubber”, the two terms being regarded assynonyms) of the “diene” type is to be understood in a known manner asan (meaning one or more) elastomer derived at least partly (i.e. ahomopolymer or a copolymer) from diene monomers (monomers bearing twocarbon-carbon double bonds, conjugated or not).

These diene elastomers can be classified into two categories:“essentially unsaturated” or “essentially saturated”. Generally, theexpression “essentially unsaturated” is understood to mean a dieneelastomer resulting at least in part from conjugated diene monomershaving a content of units of diene origin (conjugated dienes) which isgreater than 15% (mol %); thus it is that diene elastomers such as butylrubbers or diene/α-olefin copolymers of the EPDM type do not fall underthe preceding definition and may especially be described as “essentiallysaturated” diene elastomers (low or very low content of units of dieneorigin, always less than 15%). In the category of “essentiallyunsaturated” diene elastomers, the expression “highly unsaturated” dieneelastomer is understood to mean in particular a diene elastomer having acontent of units of diene origin (conjugated dienes) which is greaterthan 50%.

Although it applies to any type of diene elastomer, a person skilled inthe art of rubber articles (for example, tires) will understand that theinvention is preferably employed with essentially unsaturated dieneelastomers.

Given these definitions, the expression diene elastomer capable of beingused in the compositions in accordance with the invention is understoodin particular to mean:

-   -   (a)—any homopolymer obtained by polymerization of a conjugated        diene monomer, preferably having from 4 to 12 carbon atoms;    -   (b)—any copolymer obtained by copolymerization of one or more        conjugated dienes with one another or with one or more vinyl        aromatic compounds preferably having from 8 to 20 carbon atoms.

The following are suitable in particular as conjugated dienes:1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-di(C₁-C₅alkyl)-1,3-butadienes, such as, for example, 2,3-dimethyl-1,3-butadiene,2,3-diethyl-1,3-butadiene, 2-methyl-3-ethyl-1,3-butadiene or2-methyl-3-isopropyl-1,3-butadiene, an aryl-1,3-butadiene,1,3-pentadiene or 2,4-hexadiene. The following, for example, aresuitable as vinylaromatic compounds: styrene, ortho-, meta- orpara-methylstyrene, the “vinyltoluene” commercial mixture,para-(tert-butyl) styrene, methoxystyrenes, chlorostyrenes,vinylmesitylene, divinylbenzene or vinylnaphthalene.

The first diene elastomer may be selected from the group consisting ofpolybutadiene(s) (BR(s)), synthetic polyisoprene(s) (IR(s)), naturalrubber (NR), butadiene copolymers, isoprene copolymers and thecombinations thereof; such copolymer(s) is selected more preferably fromthe group consisting of styrene-butadiene copolymer(s) (SBR(s)) and thecombinations thereof.

The first diene elastomer may have any microstructure which depends onthe polymerization conditions used, in particular on the presence orabsence of a modifying and/or randomizing agent and on the amounts ofmodifying and/or randomizing agent employed. This elastomer may, forexample, be a block, statistical, sequential or micro sequentialelastomer and may be prepared in dispersion or in solution.

The first diene elastomer bears at least one SiOR function, R being ahydrogen atom or a hydrocarbon radical.

The expression “hydrocarbon radical” means a monovalent groupessentially consisting of carbon and hydrogen atoms. Such a group maycomprise at least one heteroatom, and it is known that the assemblyformed by the carbon and hydrogen atoms represents the major numberfraction in the hydrocarbon radical, for example alkyl or alkoxyalkyl;preferably assembly formed by the carbon and hydrogen atoms representsthe entirety of the hydrocarbon radical(s), for example alkyl. Such aSiOR (R is alkyl or alkoxyalkyl) is referred as an “alkoxysilane”function. While, a SiOH (R is a hydrogen atom) is referred as a“silanol” function.

The SiOR function borne by the first diene elastomer is not located atthe chain ends of the first diene elastomer.

According to a first variant of the first aspect, the SiOR functionborne by the first diene elastomer may be a pendant group, which isequivalent to saying that the silicon atom of the SiOR function may notbe inserted between the carbon-carbon bonds of the elastomer chain ofthe first diene elastomer. A diene elastomer bearing a pendant SiORfunction may for example be prepared by hydrosilylation of the elastomerchain by a silane bearing an alkoxysilane group, followed by hydrolysisof the alkoxysilane function to give a SiOR function.

According to a second variant of the first aspect, the SiOR functionborne by the first diene elastomer may not be a pendant group, but maybebe situated in the elastomer chain, that is, may be within the elastomerchain, which is equivalent to saying that the silicon atom of the SiORfunction may be inserted between the carbon-carbon bonds of theelastomer chain of the first diene elastomer. Such a diene elastomer maybe prepared according to the procedure described in a patent EP 2 285852 B1. This second variant is preferential and applies to the firstaspect.

A second aspect of the invention is the rubber composition according tothe first aspect, wherein the first diene elastomer is astyrene-butadiene copolymer (SBR), preferably a solutionstyrene-butadiene copolymer which is a copolymer of butadiene andstyrene, prepared in solution.

A third aspect of the invention is the rubber composition according tothe first aspect or the second aspect, wherein the first diene elastomerfurther bears at least one amine function, preferably at least onetertiary amine function.

According to a preferred embodiment of the third aspect, the aminefunction borne by the first diene elastomer may be a tertiary aminefunction. Mention will be made, as tertiary amine function, of theamines substituted with C₁-C₁₀ alkyl radicals, preferably C₁-C₄ alkyl,more preferably methyl or ethyl radical(s).

Generally, such a function borne by an elastomer, particularly a dieneelastomer, may be located on the elastomer chain end(s) or may not belocated at the elastomer chain ends, that is, may be away from the chainends. The first case occurs for example when the diene elastomer isprepared using a polymerization initiator bearing the function or usinga functionalizing agent. The second case occurs for example when thediene elastomer is modified by the use of a coupling agent orstar-branching agent bearing the function.

According to this embodiment or a preferred embodiment of the thirdaspect, the amine function borne by the first diene elastomer may be apendant group. The pendant position of the amine function means, in aknown way, that the nitrogen atom of the amine function may not beinserted between the carbon-carbon bonds of the elastomer chain of thefirst diene elastomer.

A fourth aspect of the invention is the rubber composition according tothe third aspect, wherein the SiOR function bears the amine function.

Such a diene elastomer may result from the modification of a dieneelastomer by a coupling agent that introduces, the elastomer chain, analkoxysilane group bearing an amine function according to the operatingprocedure described in a patent EP 2 285 852 B1. The following aresuitable for example as coupling agent:N,N-dialkylaminopropyltrialkoxysilanes, C₁-C₁₀, preferably C₁-C₄,dialkyl groups, the compounds3-(N,N-dimethylaminopropyl)trimethoxysilane,3-(N,N-dimethylaminopropyl)triethoxysilane,3-(N,N-diethylaminopropyl)trimethoxysilane,3-(N,N-diethylaminopropyl)triethoxysilane being most particularlypreferred, irrespective of the embodiment of the invention.

A fifth aspect of the invention is the rubber composition according toany one of the first to the fourth aspects, wherein R of the SiORfunction is a hydrocarbon radical.

According to a preferred embodiment of the fifth aspect, the hydrocarbonradical may be an alkyl radical, preferably an alkyl radical having 1 to12 carbon atoms, more preferably a branched, linear or else cyclic alkylradical having 1 to 12 carbon atoms, still more preferably 1 to 6 carbonatoms, particularly 1 to 4 carbon atoms, more particularly methyl orethyl radical(s).

A sixth aspect of the invention is the rubber composition according toany one of the first to the fifth aspects, wherein the first dieneelastomer has a glass transition temperature (Tg_(DSC)) of lower than−40° C., (for example, between −100° C. and −40° C.), advantageouslyless than −45° C. (for example, between −90° C. and −45° C.).

A seventh aspect of the invention is the rubber composition according toany one of the first to the sixth aspects, wherein the elastomer matrixoptionally comprises at least one second diene elastomer different fromthe first diene elastomer, that is, the elastomer matrix does notcomprise any second diene elastomer different from the first dieneelastomer, or the elastomer matrix further comprises at least one seconddiene elastomer different from the first diene elastomer, and whereinthe amount of the first diene elastomer is from 20 to 100 phr,preferably between 50 and 100 phr, more preferably from 55 to 95 phr,still more preferably from 60 to 90 phr, particularly from 65 to 85 phr,and wherein the amount of the second diene elastomer is 0 to 80 phr,preferably between 0 and 50 phr, more preferably from 5 to 45 phr, stillmore preferably from 10 to 40 phr, particularly from 15 to 35 phr.

According to a preferred embodiment of the seventh aspect, the seconddiene elastomer is selected from the group consisting of polybutadienes,natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprenecopolymers and the combinations thereof, preferably selected from thegroup consisting of polybutadienes and the combinations thereof.

The rubber composition according to the invention is based on areinforcing filler.

Use may be made of any type of reinforcing filler known for itscapabilities of reinforcing a rubber composition which can be used forthe manufacture of rubber articles, for example a reinforcing organicfiller, such as carbon black, or a reinforcing inorganic filler, such assilica, with which a coupling agent is combined in a known way.

According to a preferred embodiment of the invention, the amount of thereinforcing filler is more than 95 phr (for example, between 95 and 315phr), preferably more than 105 phr (for example, between 105 and 295phr), more preferably more than 115 phr (for example, between 115 and275 phr), still more preferably more than 125 phr (for example, between125 and 255 phr), particularly more than 135 phr (for example, between135 and 235 phr), more particularly more than 145 phr (for example,between 145 and 215 phr), still more particularly more than 155 phr (forexample, between 155 and 195 phr), advantageously more than 165 phr (forexample, between 165 and 175 phr).

The reinforcing filler in the rubber composition according to theinvention comprises a reinforcing inorganic filler, preferably thereinforcing filler predominately comprises the reinforcing inorganicfiller, that is, the reinforcing filler comprises more than 50%, morepreferably more than 60%, still more preferably 70%, particularly morethan 80%, more particularly more than 90%, by weight of the reinforcinginorganic filler per 100% by weight of the reinforcing filler.

The expression “reinforcing inorganic filler” should be understood hereto mean any inorganic or mineral filler, whatever its color and itsorigin (natural or synthetic), also referred to as “white filler”,“clear filler” or even “non-black filler”, in contrast to carbon black,capable of reinforcing by itself alone, without means other than anintermediate coupling agent, a rubber composition intended for themanufacture of rubber articles (for example, tires), in other wordscapable of replacing, in its reinforcing role, a conventional tire-gradecarbon black; such a filler is generally characterized, in a knownmanner, by the presence of hydroxyl (—OH) groups at its surface.

The physical state under the presence of this filler is unimportant,whether it is in the form of powder, microbeads, granules, beads or anyother suitable densified form. Of course, the reinforcing inorganicfiller of the combinations of various reinforcing inorganic fillers,preferably of highly dispersible siliceous and/or aluminous fillers isdescribed hereafter.

Mineral fillers of the siliceous type, preferably silica (SiO₂) and/orthe aluminous type, preferably alumina (Al₂O₃) are suitable inparticular as the reinforcing inorganic fillers.

An eighth aspect of the invention is the rubber composition according toany one of the first to the seventh aspects, wherein the amount of thereinforcing inorganic filler is more than 90 phr (for example, between90 and 310 phr), preferably more than 100 phr (for example, between 100and 290 phr), more preferably more than 110 phr (for example, between110 and 270 phr), still more preferably more than 120 phr (for example,between 120 and 250 phr), particularly more than 130 phr (for example,between 130 and 230 phr), more particularly more than 140 phr (forexample, between 140 and 210 phr), still more particularly more than 150phr (for example, between 150 and 190 phr), advantageously more than 160phr (for example, between 160 and 170 phr).

A ninth aspect of the invention is the rubber composition according toany one of the first to the eighth aspects, wherein the reinforcinginorganic filler predominately comprises silica, that is, thereinforcing inorganic filler comprises more than 50%, preferably morethan 75%, more preferably 100%, by weight of silica per 100% by weightof the reinforcing inorganic filer. The reinforcing inorganic filler maycomprise a type of silica or a blend of several silicas. The silica usedmay be any reinforcing silica known to a person skilled in the art, inparticular any precipitated or pyrogenic silica having a BET surfacearea and a CTAB specific surface area that are both less than 450 m²/g,preferably from 20 to 400 m²/g, more preferably from 50 to 350 m²/g,still more preferably from 100 to 300 m²/g, particularly from 150 and250 m²/g. Such silica may be covered or not.

The BET surface area is measured according to a known method, that is,by gas adsorption using the Brunauer-Emmett-Teller method described in“The Journal of the American Chemical Society”, Vol. 60, page 309,February 1938, and more specifically, in accordance with the Frenchstandard NF ISO 9277 of December 1996 (multipoint volumetric method (5points); where gas: nitrogen, degassing: 1 hour at 160° C., relativepressure range p/po: 0.05 to 0.17). The CTAB specific surface area isdetermined according to the French standard NF T 45-007 of November 1987(method B).

A person skilled in the art will understand that a reinforcing filler ofanother nature, in particular organic nature, such as carbon black,might be used as filler equivalent to the reinforcing inorganic fillerdescribed in the present section, provided that this reinforcing filleris covered with an inorganic layer, such as silica, or else comprises,at its surface, functional sites, in particular hydroxyls, requiring theuse of a coupling agent in order to form the connection between thefiller and the elastomer. By way of example, mention may be made ofcarbon blacks for rubber articles (for example, tires), such asdescribed in patent applications WO 96/37547 and WO 99/28380.

A tenth aspect of the invention is the rubber composition according toany one of the first to the ninth aspects, wherein the reinforcingfiller further comprises carbon black, and wherein the amount of carbonblack is less than 10 phr (for example, between 0 and 10 phr),preferably less than 9 phr (for example, between 1 and 9 phr), morepreferably less than 8 phr (for example, between 2 and 8 phr).

Within the ranges indicated, there is a benefit of coloring properties(black pigmentation agent) and anti-UV properties of carbon blacks,without furthermore adversely affecting the typical performance providedby the reinforcing inorganic filler, namely low hysteresis (reducedrolling resistance).

In order to couple the reinforcing inorganic filler to the elastomermatrix, for instance, the diene elastomer, use can be made, in a knownmanner, of a coupling agent (or bonding agent) intended to provide asatisfactory connection, of chemical and/or physical nature, between thereinforcing inorganic filler (surface of its particles) and theelastomer matrix, for instance, the diene elastomer. This coupling agentis at least bifunctional. Use can be made in particular of at leastbifunctional organosilanes or polyorganosiloxanes.

Use can be made in particular of silane polysulphides, referred to as“symmetrical” or “asymmetrical” depending on their particular structure,as described, for example, in applications WO 03/002648, WO 03/002649and WO 2004/033548.

Particularly suitable silane polysulphides correspond to the followinggeneral formula (I):

Z-A-Sx-A-Z,   (I)

in which:

-   -   x is an integer from 2 to 8 (preferably from 2 to 5);    -   A is a divalent hydrocarbon radical (preferably, C₁-C₁₈ alkylene        groups or C₆-C₁₂ arylene groups, more particularly C₁-C₁₀, in        particular C₁-C₄, alkylenes, especially propylene);    -   Z corresponds to one of the formulae below:

in which:

-   -   the R¹ radicals which are unsubstituted or substituted and        identical to or different from one another, represent a C₁-C₁₈        alkyl, C₅-C₁₈ cycloalkyl or C₆-C₁₈ aryl group (preferably, C₁-C₆        alkyl, cyclohexyl or phenyl groups, in particular C₁-C₄ alkyl        groups, more particularly methyl and/or ethyl),    -   the R² radicals which are unsubstituted or substituted and        identical to or different from one another, represent a C₁-C₁₈        alkoxyl or C₅-C₁₈ cycloalkoxyl group (preferably a group        selected from C₁-C₈ alkoxyls and C₅-C₈ cycloalkoxyls, more        preferably a group selected from C₁-C₄ alkoxyls, in particular        methoxyl and ethoxyl), are suitable in particular, without        limitation of the above definition.

In the case of a mixture of alkoxysilane polysulphides corresponding tothe above formula (I), in particular normal commercially availablecombinations, the mean value of the “x” indices is a fractional numberpreferably of between 2 and 5, more preferably of approximately 4.However, the present invention can also advantageously be carried out,for example, with alkoxysilane disulphides (x=2).

Mention will more particularly be made, as examples of silanepolysulphides, ofbis((C₁-C₄)alkoxyl(C₁-C₄)alkylsilyl(C₁-C₄)alkyl)polysulphides (inparticular disulphides, trisulphides or tetrasulphides), such as, forexample, bis(3-trimethoxysilylpropyl) orbis(3-triethoxysilylpropyl)polysulphides. Use is in particular made,among these compounds, of bis(3-triethoxysilylpropyl)tetrasulphide,abbreviated to TESPT, of formula [(C₂H₅O)₃Si(CH₂)₃S₂]₂, orbis(3-triethoxysilylpropyl)disulphide, abbreviated to TESPD, of formula[(C₂HSO)₃Si(CH₂)₃S]₂. Mention will also be made, as preferred examples,of bis(mono(C₁-C₄)alkoxyldi(C₁-C₄)alkyl silylpropyl)polysulphides (inparticular disulphides, trisulphides or tetrasulphides), moreparticularly bis(monoethoxydimethylsilylpropyl)tetrasulphide, asdescribed in patent application WO 02/083782 (or U.S. Pat. No.7,217,751).

Mention will in particular be made, as coupling agent other thanalkoxysilane polysulphide, of bifunctional POSs (polyorganosiloxanes) orof hydroxysilane polysulphides (R²=OH in the above formula (I)), such asdescribed in patent applications WO 02/30939 (or U.S. Pat. No.6,774,255) and WO 02/31041 (or US 2004/051210), or of silanes or POSscarrying azodicarbonyl functional groups, such as described, forexample, in patent applications WO 2006/125532, WO 2006/125533 and WO2006/125534.

As examples of other silane sulphides, mention will be made, forexample, of the silanes bearing at least one thiol (—SH) function(referred to as mercaptosilanes) and/or at least one blocked thiolfunction, such as described, for example, in patents or patentapplications U.S. Pat. No. 6,849,754, WO 99/09036, WO 2006/023815, WO2007/098080, WO 2008/055986 and WO 2010/072685.

Of course, use could also be made of combinations of the coupling agentsdescribed previously, as described in particular in the aforementionedpatent application WO 2006/125534.

According to a preferred embodiment of the invention, the content ofcoupling agent is from 0.5 to 15% by weight per 100% by weight of thereinforcing inorganic filler, particularly silica.

According to a preferred embodiment of the invention, the rubbercomposition of the tread of the rubber composition according to theinvention is based on less than 50 phr (for example, between 0 and 50phr), preferably less than 40 phr (for example, between 1 and 40 phr),more preferably more less than 30 phr (for example, between 2 and 30phr), of coupling agent.

The rubber composition according to the invention is based on aplasticizing agent.

The role of the plasticizing agent is to soften the matrix by dilutingthe elastomer and the reinforcing filler.

According to a preferred embodiment of the invention, the amount of theplasticizing agent is more than 45 phr (for example, between 45 and 205phr), preferably more than 55 phr (for example, between 55 and 195 phr),more preferably more than 65 phr (for example, between 65 and 185 phr),still more preferably more than 75 phr (for example, between 75 and 175phr), particularly more than 85 phr (for example, between 85 and 165phr), particularly more than 95 phr (for example, between 95 and 155phr), more particularly more than 105 phr (for example, between 105 and145 phr), still more particularly more than 115 phr (for example,between 115 and 135 phr).

The plasticizing agent in the rubber composition according to theinvention comprises the liquid plasticizer.

The liquid plasticizer is liquid at 20° C. by definition, and itsTg_(DSC) is by definition less than −20° C., preferably less than −30°C., more preferably less than −40° C.

Any extending oil, whether of aromatic or non-aromatic nature, anyliquid plasticizing agent known for its plasticizing properties withregard to elastomer matrix(es) (for instance, diene elastomer), can beused as the liquid plasticizer. At ambient temperature (20° C.) underatmospheric pressure, these plasticizers or these oils, which are moreor less viscous, are liquids (that is to say, as a reminder, substancesthat have the ability to eventually take on the shape of theircontainer), as opposite to plasticizing hydrocarbon resin(s) which areby nature solid at ambient temperature (20° C.) under atmosphericpressure.

According to a preferred embodiment of the invention, the amount of theliquid plasticizer is more than 10 phr (for example, between 10 and 90phr), preferably more than 20 phr (for example, between 20 and 80 phr),more preferably more than 30 phr (for example, between 30 and 70 phr),still more preferably more than 40 phr (for example, between 40 and 60phr).

The liquid plasticizer in the plasticizing agent in the rubbercomposition according to the invention comprises a liquid diene polymer.

The liquid diene polymer is a diene polymer, and is liquid at 20° C. bydefinition.

An eleventh aspect of the invention is the rubber composition accordingto any one of the first to the tenth aspects, wherein the amount of theliquid diene polymer is at most 25 phr (for example, from 1 to 25 phr),preferably at most 20 phr (for example, from 3 to 20 phr), morepreferably at most 15 phr (from 5 to 15 phr).

A twelfth aspect of the invention is the rubber composition according toany one of the first to the eleventh aspects, wherein the liquid dienepolymer has a glass transition temperature of less than −60° C. (forexample, between −100° C. and −60° C.), preferably less than −65° C.(for example, between −95° C. and −65° C.), more preferably less than−70° C. (for example, between −90° C. and −70° C.), still morepreferably less than −75° C. (for example, between −85° C. and −75° C.).

A thirteenth aspect of the invention is the rubber composition accordingto any one of the first to twelfth aspects, wherein the liquid dienepolymer has a number average molar mass of less than 6000 g/mol (forexample, between 500 and 6000 g/mol), preferably less than 5500 g/mol(for example, between 1000 and 5500 g/mol), more preferably less than5000 g/mol (for example, between 1500 and 5000 g/mol), still morepreferably less than 4000 g/mol (for example, between 2000 and 4000g/mol).

The number average molar mass (Mn) can be measured by gel permeationchromatography (GPC).

In case of gel permeation chromatography (GPC) of hydroxyl-terminatedpolybutadienes: The measurements can be carried out at 40° C. intetrahydrofuran (THF) at a concentration of 1 g/L and a flow rate of 0.3ml/min. Chromatographic separation can be achieved using a PSS SDV Micro5μ/4.6×30 mm precolumn and a PSS SDV Micro linear S 5μ/4.6×250 mm (2×)separation column. Detection can be by means of an RI detector.Calibration can be carried out by means of a polybutadiene standard(PSS-Kit polybutadiene-1,4, Mp 83 1-106000, Part No. :PSS-bdfkit, Mn:1830/4330/9300/18000/33500).

In cast of gel permeation chromatography (GPC) of silane terminatedpolybutadienes: The measurements can be carried out at room temperaturein tetrahydrofuran (THF) at a concentration of 5 g/L and a flow rate of1 ml/min. Chromatographic separation can be effected using a combinationof styrene-divinylbenzene columns (2×3 cm, 5 μn, linear; 1×30 cm 5 μm,100 Å). Detection can be by means of an RI detector. Calibration can becarried out by means of polystyrene standards and absolute molecularweights obtained via Mark-Houwink constants (a=0.73; k=0.0266 ml/g).

According to a preferred embodiment of the invention, the liquid dienepolymer is selected from the group consisting of liquidpolybutadiene(s), liquid polyisoprene(s), liquid styrene-butadienecopolymer(s), and the combinations thereof.

According to a more preferred embodiment of the preferred embodiment,the liquid diene polymer is preferably selected from the groupconsisting of liquid polybutadiene(s), liquid polyisoprene(s), and thecombinations thereof.

According to another more preferred embodiment of the preferredembodiment, the liquid diene polymer is preferably selected from thegroup consisting of liquid polybutadiene(s), liquid styrene-butadienecopolymer(s), and the combinations thereof.

A fourteenth aspect of the invention is the rubber composition accordingto any one of the first to thirteenth aspects, wherein the liquid dienepolymer comprises the 1,3-butadiene derived monomer units being1,2-vinyl, 1,4-trans and 1,4-cis, and wherein the proportion of1,2-vinyl in the entirety of the 1,3-butadiene derived monomer unitspresent in the liquid diene polymer is less than 40 mol % (for example,between 0 and 40 mol %), preferably less than 35 mol % (for example,between 5 and 35 mol %), more preferably less than 30 mol % (forexample, between 10 and 30 mol %), and wherein the sum of theproportions of 1,4-trans and 1,4-cis in the entirety of the1,3-butadiene derived monomer units present in the liquid diene polymeris more than 60 mol % (for example, between 60 and 100 mol %),preferably more than 65 mol % (for example, between 65 and 95 mol %),more preferably more than 70 mol % (between 70 and 90 mol %).

According to a preferred embodiment of the fourteenth aspect, whereinthe proportion of 1,4-trans in the entirety of the 1,3-butadiene derivedmonomer units present in the liquid diene polymer is more than 30 mol %(for example, between 30 and 90 mol %), preferably more than 35 mol %(for example, between 35 and 85 mol %), more preferably more than 40%(for example, between 40 and 80 mol %), still more preferably more than45% (for example, between 45 and 75 mol %), particularly more than 50mol % (for example, between 50 and 70 mol %).

The features of the above microstructure (1,2-vinyl content; 1,4-ciscontent; and 1,4-trans content) can be determined after completion ofsynthesis of the liquid diene polymer by nuclear magnetic resonance(NMR) with ¹H, ¹³C or the both, for example, ¹³C NMR (90.5628 MHz;relaxation agent: Cr (acac)₃; solvent: deuterated chloroform (CDC₁₃),Bruker 360 MHz).

A fifteenth aspect of the invention is the rubber composition accordingto any one of the first to the fourteenth aspects, wherein the liquiddiene polymer is a liquid polybutadiene.

According to a preferred embodiment of the fifteenth aspect, the term“liquid polybutadiene” as used herein is to be understood as meaning aproduct obtainable by polymerization of monomer units each having atleast two conjugated double bonds, wherein in order of increasingpreference, at least 80, 85, 90, 95, 98, 99 or 99.9% of the monomerunits are 1,3-butadiene.

The liquid diene polymer in the liquid plasticizer in the plasticizingagent in the rubber composition according to the invention bears atleast one function.

A sixteenth aspect of the invention is the rubber composition accordingto any one of the first to the fifteenth aspects, wherein the liquiddiene polymer is such that the function comprises at least one functionselected from the group consisting of silane function(s), hydroxylfunction(s), anhydride function(s) (for example, maleic anhydridefunctions), and the combinations thereof.

According to a preferred embodiment of the invention, the liquid dienepolymer has an average functionality of more than 1.0 (for example,between 1.0 and 4.0), preferably at least 2.0 (from 2.0 to 3.0). Theaverage functionality can be calculated via the number average molarmass (Mn) of the liquid diene polymer and the function number (forexample, the number of silane groups, the number of hydroxyl groups, andthe number of anhydride groups).

According to a preferred embodiment of the sixteenth aspect, the liquiddiene polymer is such that the function comprises at least one functionselected from the group consisting of silane function(s), hydroxylfunction(s), and the combinations thereof.

According to a more preferred embodiment of the sixteenth aspect or thepreferred embodiment, the liquid diene polymer is a liquid diene polymerproduced by free-radical polymerization.

According to a still more preferred embodiment of the more preferredembodiment, the liquid diene polymer is a liquid polybutadiene thatcomprises at least one hydroxyl function produced by polymerization of1,3-butadiene in the presence of peroxide, water and an organic solvent,preferably the liquid polybutadiene is a hydroxyl-terminated liquidpolybutadiene, as described in EP12169794,

According to another still more preferred embodiment of the morepreferred embodiment, the liquid diene polymer a liquid polybutadienethat comprises at least one silane function produced by reacting atleast one organosilane compound (preferably,3-isocyanatopropyltrimethoxysilane, isocyanatopropyltriethoxysilane orthe combinations thereof) with the liquid polybutadiene comprising atleast one hydroxyl function (preferably, a hydroxyl-terminated liquidpolybutadiene), preferably a triethoxysilane-terminated liquidpolybutadiene, as described in EP3294574.

A seventeenth aspect of the invention is the rubber compositionaccording to any one of the first to the sixteenth aspects, wherein theliquid diene polymer is such that the function is a silane function.

According to a preferred embodiment of the invention, the liquidplasticizer optionally comprises at least one liquid plasticizer otherthan the liquid diene polymer, that is, the liquid plasticizer does notcomprise any liquid plasticizer other than the liquid diene polymer, orcomprises at least one liquid plasticizer other than the liquid dienepolymer. Preferably, the liquid plasticizer other than the liquid dienepolymer is selected from the group consisting of liquid diene polymer(s)not bearing any function, polyolefinic oil(s), naphthenic oil(s),paraffinic oil(s), Distillate Aromatic Extracts (DAE) oil(s), MediumExtracted Solvates (MES) oil(s), Treated Distillate Aromatic Extracts(TDAE) oil(s), Residual Aromatic Extracts (RAE) oil(s), Treated ResidualAromatic Extracts (TRAE) oil(s), Safety Residual Aromatic Extracts(SRAE) oil(s), mineral oil(s), vegetable oil(s), ether plasticizer(s),ester plasticizer(s), phosphate plasticizer(s), sulphonateplasticizer(s) and the combinations thereof, preferably selected fromthe group consisting of IVIES oils, TDAE oils, naphthenic oils,vegetable oils and the combinations thereof, more preferably selectedfrom the group consisting of MES oils, vegetable oils and thecombinations thereof, still more preferably selected from the groupconsisting of vegetable oils and the combinations thereof.

An eighteenth aspect of the invention is the rubber compositionaccording to any one of the first to the seventeenth aspects, whereinthe liquid plasticizer further comprises a vegetable oil, and whereinthe amount in phr of vegetable oil is higher than one-third of theamount in phr of the liquid diene polymer.

According to a preferred embodiment of the eighteenth aspect, the amountin phr of vegetable oil is higher than that of the liquid diene polymer,preferably the amount in phr of vegetable oil is higher than twice ofthe amount in phr of the liquid diene polymer.

According to a preferred embodiment of the eighteenth aspect, the amountof the vegetable oil is more than 5 phr (for example, between 5 and 65phr), preferably more than 10 phr (for example, between 10 and 60 phr),more preferably more than 15 phr (for example, between 15 and 55 phr),still more preferably more than 20 phr (for example, between 20 and 50phr), particularly more than 25 phr (for example, between 25 and 45phr), more particularly more than 30 phr (for example, between 30 and 40phr).

According to a preferred embodiment of the eighteenth aspect, thevegetable oil(s) is made of an oil selected from the group consisting oflinseed, safflower, soybean, corn, cottonseed, turnip seed, castor,tung, pine, sunflower, palm, olive, coconut, groundnut and grapeseedoils, and the combinations thereof, preferably sunflower oil(s), morepreferably sunflower oil(s) containing over 60%, still preferably moreover 70%, particularly over 80%, more particularly over 90%, still moreparticularly 100%, by weight of oleic acid.

A nineteenth aspect of the invention is the rubber composition accordingto any one of the first to the eighteenth aspects, wherein theplasticizing agent further comprises a hydrocarbon resin, and whereinthe amount in phr of hydrocarbon resin is higher than that of the liquiddiene polymer.

According to a preferred embodiment of the nineteenth aspect, the amountin phr of hydrocarbon resin is higher than twice of the amount in phr ofthe liquid diene polymer, preferably the amount in phr of hydrocarbonresin is higher than triple of the amount in phr of the liquid dienepolymer.

According to a preferred embodiment of the nineteenth aspect, the amountin phr of hydrocarbon resin is higher than the total amount in phr ofthe liquid plasticizer.

According to a preferred embodiment of the nineteenth aspect, the amountof the hydrocarbon resin is more than 10 phr (for example, between 10and 150 phr), preferably more than 15 phr (for example, between 15 and145 phr), more preferably more than 20 phr (for example, between 20 and140 phr), still more preferably more than 25 phr (for example, between24 and 135 phr), particularly more than 30 phr (for example, between 30and 130 phr), more particularly more than 35 phr (for example, between35 and 125 phr), still more particularly more than 40 phr (for example,between 40 and 120 phr), advantageously more than 45 phr (for example,between 45 and 115 phr), more advantageously more than 50 phr (forexample, between 50 and 110 phr), still more advantageously more than 55phr (for example, between 55 and 105 phr), especially more than 60 phr(for example, between 60 and 100 phr), more especially more than 65 phr(for example, between 65 and 95 phr), still more especially more than 70phr (for example, between 70 and 90 phr).

The hydrocarbon resin(s) are polymer well known by a person skilled inthe art, which are essentially based on carbon and hydrogen, and thusmiscible by nature in rubber composition(s), for instance, dieneelastomer composition(s). They can be aliphatic or aromatic or also ofthe aliphatic/aromatic type, that is to say based on aliphatic and/oraromatic monomers. They can be natural or synthetic and may or may notbe petroleum-based (if such is the case, also known under the name ofpetroleum resins). They are preferably exclusively hydrocarbon, that isto say, that they comprise only carbon and hydrogen atoms.

Preferably, the hydrocarbon resins as being “plasticizing” exhibit atleast one, more preferably all, of the following characteristics:

-   -   a Tg_(DSC) of above 20° C. (for example between 20° C. and 100°        C.), preferably above 30° C. (for example between 30° C. and        100° C.), more preferably above 40° C. (for example between        40° C. and 100° C.);    -   a number-average molecular weight (Mn) of between 400 and 2000        g/mol (more preferably between 500 and 1500 g/mol);    -   a polydispersity index (PI) of less than 3, more preferably less        than 2 (reminder: PI=Mw/Mn with Mw the weight-average molecular        weight).

The macrostructure (Mw, Mn and PI) of the hydrocarbon resins isdetermined by steric exclusion chromatography (SEC): solventtetrahydrofuran; temperature 35 ; concentration 1 g/l; flow rate 1ml/min; solution filtered through a filter with a porosity of 0.45 μmbefore injection; Moore calibration with polystyrene standards; set of 3“Waters” columns in series (“Styragel” HR4E, HR1 and HR0.5); detectionby differential refractometer (“Waters 2410”) and its associatedoperating software (“Waters Empower”).

According to preferred embodiment of the nineteenth aspect, thehydrocarbon resin is selected from the group consisting ofcyclopentadiene (abbreviated to CPD) homopolymer or copolymer resins,dicyclopentadiene (abbreviated to DCPD) homopolymer or copolymer resins,terpene homopolymer or copolymer resins, C₅ fraction homopolymer orcopolymer resins, C₉ fraction homopolymer or copolymer resins,alpha-methyl styrene homopolymer or copolymer resins and thecombinations thereof. Use is more preferably made, among the abovecopolymer resins, of those selected from the group consisting of(D)CPD/vinylaromatic copolymer resins, (D)CPD/terpene copolymer resins,(D)CPD/C₅ fraction copolymer resins, (D)CPD/C₉ fraction copolymerresins, terpene/vinylaromatic copolymer resins, terpene/phenol copolymerresins, C₅ fraction/vinyl-aromatic copolymer resins, C₉fraction/vinylaromatic copolymer resins, and the combinations thereof.

The term “terpene” combines here, in a known way, the α-pinene, β-pineneand limonene monomers; use is preferably made of a limonene monomer,which compound exists, in a known way, in the form of three possibleisomers: L-limonene (laevorotatory enantiomer), D-limonene(dextrorotatory enantiomer) or else dipentene, the racemate of thedextrorotatory and laevorotatory enantiomers. Styrene, α-methylstyrene,ortho-, meta- or para-methylstyrene, vinyltoluene,para-(tert-butyl)styrene, methoxystyrenes, chlorostyrenes,hydroxystyrenes vinylmesitylene, divinylbenzene, vinylnaphthalene, orany vinylaromatic monomer resulting from a C₉ fraction (or moregenerally from a C₈ to C₁₀ fraction) are suitable, for example, asvinylaromatic monomer. Preferably, the vinylaromatic compound is styreneor a vinylaromatic monomer resulting from a C₉ fraction (or moregenerally from a C₈ to C₁₀ fraction). Preferably, the vinylaromaticcompound is the minor monomer, expressed as molar fraction, in thecopolymer under consideration.

Mention may also be made, as examples of other preferred resins, ofphenol-modified α-methylstirene resins. It should be remembered that, inorder to characterize these phenol-modified resins, use is made, in aknown way, of a number referred to as “hydroxyl number” (measuredaccording to Standard ISO 4326 and expressed in mg KOH/g).α-Methylstirene resins, in particular those modified with phenol, arewell known to a person skilled in the art and are availablecommercially.

The rubber compositions according to the invention may be based on allor a portion(s) of the usual additives generally used in the elastomercompositions intended in particular for rubber articles (for example,tires, shoes or caterpillar tracks), in more particular for tires, instill more particular for tire treads, such as, for example, protectionagents, such as antiozone waxes, chemical antiozonants, antioxidants,reinforcing resins, methylene acceptors (for example phenolic novolakresin) or methylene donors (for example hexamethylenetetramine (HMT) orhexamethoxymethylmelamine (H3M)), a crosslinking system based either onsulphur or on donors of sulphur and/or per oxide and/or bismaleimides,vulcanization accelerators, or vulcanization activators.

The composition can be also based on coupling activators when a couplingagent is used, agents for covering the reinforcing inorganic filler ormore generally processing aids capable, in a known way, by virtue of animprovement in the dispersion of the filler in the rubber matrix and ofa lowering of the viscosity of the compositions, of improving theirproperty of processing in the raw state; these agents are, for example,hydrolysable silanes, such as alkylalkoxysilanes, polyols, polyethers,amines, or hydroxylated or hydrolysable polyorganosiloxanes.

The rubber composition according to the invention may be manufactured inappropriate mixers using two successive preparation phases well known toa person skilled in the art: a first phase of thermomechanical workingor kneading (referred to as “non-productive” phase) at high temperature,up to a maximum temperature of between 110° C. and 190° C., preferablybetween 130° C. and 180° C., followed by a second phase of mechanicalworking (referred to as “productive” phase) at a lower temperature,typically of less than 110° C., for example between 40° C. and 100° C.,finishing phase during which the crosslinking or vulcanization system isincorporated.

A process which can be used for the manufacture of such compositionscomprises, for example and preferably, the following steps:

-   -   incorporating in the elastomer matrix, for instance, the diene        elastomer(s), in a mixer, the reinforcing filler, the        plasticizing agent during a first stage (“non productive” stage)        everything being kneaded thermomechanically (for example in one        or more steps) until a maximum temperature of between 110° C.        and 190° C. is reached;    -   cooling the combined mixture to a temperature of less than 100°        C.;    -   subsequently incorporating, during a second stage (referred to        as a “productive” stage), a crosslinking system;    -   kneading everything up to a maximum temperature of less than        110° C.;    -   extruding or calendering the rubber composition thus obtained,        in particular in the form of a tire tread.

According to a preferred embodiment of the invention, the first(non-productive) phase is carried out in a single thermomechanical stageduring which all the necessary constituents may be introduced into anappropriate mixer, such as a standard internal mixer, followed, in asecond step, for example after kneading for 1 to 2 minutes, by the otheradditives, optional additional filler-covering agents or processingaids, with the exception of the crosslinking system. The total kneadingtime, in this non-productive phase, is preferably between 1 and 15 min.

After cooling the mixture thus obtained, the crosslinking system may bethen incorporated at low temperature (for example, between 40° C. and100° C.), generally in an external mixer, such as an open mill; thecombined mixture is then mixed (the second (productive) phase) for a fewminutes, for example between 2 and 15 min.

The crosslinking system is preferably based on sulphur and on a primaryvulcanization accelerator, in particular on an accelerator ofsulphenamide type. Added to this vulcanization system are various knownsecondary accelerators or vulcanization activators, such as zinc oxide,stearic acid, guanidine derivatives (in particular diphenylguanidine),and the like, incorporated during the first non-productive phase and/orduring the productive phase. The content of sulphur is preferablybetween 0.5 and 10.0 phr, more preferably between 0.5 and 3.0 phr, andthat of the primary accelerator is preferably between 0.5 and 5.0 phr.

Use may be made, as accelerator (primary or secondary) of any compoundcapable of acting as accelerator of the vulcanization of elastomermatrix, for instance, diene elastomers, in the presence of sulphur, inparticular accelerators of the thiazoles type and their derivatives,accelerators of thiurams types, or zinc dithiocarbamates. Theseaccelerators are more preferably selected from the group consisting of2-mercaptobenzothiazyl disulphide (abbreviated to “MBTS”),N-cyclohexyl-2-benzothiazole sulphenamide (abbreviated to “CBS”),N,N-dicyclohexyl-2 benzothiazolesulphenamide (“DCBS”),N-tert-butyl-2-ben zothiazolesulphenamide (“TBBS”), N-tert-butyl-2benzothiazolesulphenimide (“TBSP”), zinc dibenzyldithiocarbamate(“ZBEC”), Tetrabenzylthiuram disulfide (“TBZTD”) and the combinationsthereof.

The final composition thus obtained is subsequently calendered, forexample in the form of a sheet or of a plaque, in particular forlaboratory characterization, or else extruded in the form of a rubberprofiled element which can be used directly as a laminate or an article,for example, a tire tread, a shoe sole and a caterpillar track tread.

The vulcanization (or curing) is carried out in a known way at atemperature generally of between 110° C. and 190° C. for a sufficienttime which may vary, for example, between 5 and 90 min depending inparticular on the curing temperature, the vulcanization system adoptedand the vulcanization kinetics of the composition under consideration.

According to a preferred embodiment of the invention, an articlecomprises a rubber composition according to any one of the first to thenineteenth aspects.

According to a more preferred embodiment of the preferred embodiment,the article is a tire, a shoe, a conveyor or a caterpillar track, forexample, a tire tread, a shoe sole, a conveyor belt and a caterpillartrack tread.

According to a still more preferred embodiment of the more preferredembodiment, the article is a tire, preferably a tire in which the rubbercomposition according to any one of the first to the nineteenth aspectsis comprised in its tread, sidewall(s) or the both.

The tires of the invention are particularly intended to equip passengermotor vehicles, including 4×4 (four-wheel drive) vehicles and SUV (SportUtility Vehicles) vehicles, and industrial vehicles particularlyselected from vans and heavy duty vehicles (i.e., bus or heavy roadtransport vehicles (lorries, tractors, trailers)).

A twentieth aspect of the invention is a tire tread comprising a rubbercomposition according to any one of the first to the nineteenth aspects.

According to a preferred embodiment of twentieth aspect, the tire treadcomprising at least two radially superposed portions which comprises aradially external portion and a radially internal portion, the radiallyexternal portion intended to come into contact with the ground, theradially external portion being made of a first rubber composition, andthe radially internal portion being made of a second rubber compositiondifferent from the first rubber composition.

According to a more preferred embodiment of the preferred embodiment,the first rubber composition is a rubber composition any one of thefirst to the nineteenth aspects.

According to another more preferred embodiment of the preferredembodiment, the second rubber composition is a rubber composition anyone of the first to the nineteenth aspects.

According to an embodiment of the other more preferred embodiment, theradially external portion is intended to come into contact with theground during service life of the tire.

According to another embodiment of the other more preferred embodiment,the radially external portion is not intended to come into contact withthe ground during service life of the tire.

A radial direction is defined as a direction perpendicular to the axisof rotation of the tire, and the expression “radially” means “in radialdirection”. The expressions “radially on the inside (radially inner orradially internal), or respectively radially on the outside (radiallyouter or radially external)” mean “closer or, respectively, furtheraway, from the axis of rotation of the tire, in the radial direction,than”.

The service life of the tire means the duration to use the tire (forexample, the term from the new state to the final state of the tire, thefinal state means a state on reaching the wear indicator bar(s) in thetread of tire).

The invention relates to the rubber compositions in the raw state (i.e.,before curing) and in the cured state (i.e., after crosslinking orvulcanization).

The invention is further illustrated by the following non-limitingexamples.

EXAMPLE

In order to confirm the effect of the invention, four rubbercompositions (identified as C-1 (a reference), C-2 and C-3 (examplesaccording to the invention), and C-4 (a comparative example)) arecompared for Mooney plasticity (as an index of processability beforecuring) and tan(δ)_(max) (as an index of hysteresis property aftercuring). They are based on a blend of BR and SBR bearing a SiOR function(as an elastomer matrix) reinforced with a blend of silica (as areinforcing inorganic filler) and carbon black, and a plasticizing agentcomprising a liquid polybutadiene (as a liquid diene polymer), asunflower oil (as vegetable oil) and a C_(5/)C₉ hydrocarbon resin (ashydrocarbon resin. The formulations of the three rubber compositions aregiven at Table 1 with the content of the various products expressed inphr.

-   -   C-1: based on SBR bearing a SiOR function not located at the        elastomer chain end, with non-functionalized liquid        polybutadiene (a reference);    -   C-2: based on SBR bearing a SiOR function not located at the        elastomer chain end, with a hydroxyl-terminated liquid        polybutadiene (an example according to the invention);    -   C-3: based on SBR bearing a SiOR function not located at the        elastomer chain end, with a triethoxysilane-terminated liquid        polybutadiene (an example according to the invention);    -   C-4: based on SBR bearing a SiOR function located at the        elastomer chain end, with a triethoxysilane-terminated liquid        polybutadiene (a comparative example according to the        invention).

Each rubber composition was produced as follows: The reinforcing filler,its associated coupling agent, the plasticizing agent, the elastomermatrix and the various other ingredients, with the exception of thevulcanization system, were successively introduced into an internalmixer having an initial vessel temperature of approximately 60° C.; themixer was thus approximately 70% full (% by volume). Thermomechanicalworking (non-productive phase) was then carried out in one stage, whichlasts in total approximately 3 to 4 minutes, until a maximum “dropping”temperature of 165° C. was reached. The mixture thus obtained wasrecovered and cooled and then sulphur and an accelerator of sulphenamidetype were incorporated on an external mixer (homofinisher) at 20 to 30°C., everything being mixed (productive phase) for an appropriate time(for example, between 5 and 12 min).

The rubber compositions thus obtained were subsequently calendered,either in the form of sheets (thickness of 2 to 3 mm) or of fine sheetsof rubber, for the measurement of their physical or mechanicalproperties, or in the form of profiled elements which could be useddirectly, after cutting and/or assembling to the desired dimensions, forexample as tire semi-finished products, in particular as tire treads.

As the measurement of Mooney plasticity of each rubber compositionbefore curing, the use was made of an oscillating consistometer asdescribed in French Standard NF T 43-005 (November 1980). The Mooneyplasticity measurement was carried out according to the followingprinciple: the composition in the raw state (before curing) was moldedin a cylindrical chamber heated to 100° C. After preheating for oneminute, the rotor rotated within the test specimen at 2revolutions/minute and the working torque for maintaining this movementwas measured after rotating for 4 minutes. The Mooney plasticity (ML1+4)is generally expressed in “Mooney unit” (MU, With 1 MU: 0.83Newton-meter), and is representative of the processability. The lowerMooney plasticity is, the better processability is, therefore, a value(Mooney plasticity (C-1)/Mooney plasticity (C-n)×100; where n=1, 2, 3and 4) greater than that of the reference (C-1), set at 100, indicatesan improved performance.

Each rubber composition was placed in a press with heated platens at atemperature (typically 160° C.), and for the time that was necessary forthe crosslinking of these rubber compositions (typically several tens ofminutes), at a pressure (typically 16 bar), and then, that is aftercuring, tan(δ)_(max) of Each rubber composition was measured on aviscosity analyser (Metravib VA4000), according to the standard ASTM D5992-96. A recording was made of the response of a sample of vulcanizedcomposition (cylindrical test specimen with a thickness of 4 mm and across section of 400 mm²), subjected to a simple alternating sinusoidalshear stress, at the frequency of 10 Hz, under defined temperatureconditions, for example at 23° C. according to the standard ASTM D1349-99. A strain amplitude sweep was carried out from 0.1% to 100%(outward cycle), then from 100% to 1% (return cycle). For the returncycle, the maximum value of tan(δ) observed, identified as tan(δ)_(max)at 23° C., was indicated. The value of tan(δ)_(max) at 23° C. isrepresentative of the hysteresis property, and therefore of the rollingresistance. The lower tan(δ)_(max) at 23° C. is, the better thehysteresis property (relative to rolling resistance) is, therefore, avalue (tan(δ)_(max) (C-1)/tan(δ)_(max) (C-n)×100; where n=1, 2, 3 and 4)greater than that of the reference (C-1), set at 100, indicates animproved performance.

The results from Table 1 demonstrate that the rubber compositions (C-2and C-3) according to the invention have an unexpectedly improvedbalance of performances between the processability and the hysteresisproperty than that of the reference or the comparative example (C-1 andC-4). The balance between the processability and the hysteresis propertyin Table 1 is a sum of the both performances.

In conclusion, the rubber composition according to the invention allowsan improvement of the balance of performances between the processabilityand the hysteresis property.

TABLE 1 Comparative Reference Example Example example C-1 C-2 C-3 C-4SBR1 (1) 70 70 70 SBR2 (2) 70 BR (3) 30 30 30 30 Carbon black (4) 4 4 44 Silica (5) 165 165 165 165 Coupling agent (6) 13 13 13 13 Liquid diene10 polymer 1 (7) Liquid diene 10 polymer 2 (8) Liquid diene 10 10polymer 3 (9) Vegetable oil (10) 37 37 37 37 Hydrocarbon 80 80 80 80resin (11) ZnO 3 3 3 3 Stearic acid 3 3 3 3 Antiozone wax 3 3 3 3Antioxidant (12) 3 3 3 3 DPG (13) 2 2 2 2 Sulphur 2 2 2 2 Accelerator(14) 3 3 3 3 Mooney plasticity 100 100 104 83 Tan( δ )max 100 103 123110 Balance of 200 203 227 193 performances

-   -   (1) SBR1: solution SBR with 16% of styrene unit and 24% of unit        1,2 of the butadiene part (Tg_(DSC)=−65° C.) bearing a SiOR        function, R being a methyl radical, the SiOR function not        located at the ends of the elastomer chain; wherein the silicon        atom of the SiOR function is inserted between the carbon-carbon        bonds of the elastomer chain; the SBR further bearing a tertiary        amine function made of the amine substituted with two methyl        radicals; wherein the nitrogen atom of the amine function is not        inserted between the carbon-carbon of the elastomer chain, and        the SiOR function bears the amine function; the SBR prepared        according to a process described in a patent EP 2 285 852 B1;    -   (2) SBR2: solution SBR with 16% of styrene unit and 24% of unit        1,2 of the butadiene part (Tg_(DSC)=−65° C.) bearing a SiOR        function, R being a hydrogen atom, the SiOR being        dimethylsilanol function at the end of the elastomer chain, the        SBR prepared according to a process described in a patent EP 0        778 311 B 1;    -   (3) BR: BR with 0.3% of 1,2-vinyl; 2.7% of 1,4-trans; 97% of        1,4-cis (Tg_(DSC)=−105° C.);    -   (4) Carbon black: Carbon black (ASTM grade N234 from Cabot);    -   (5) Silica: Silica (“Zeosil 1165MP” from Rhodia (CTAB, BET:        about 160 m²/g));    -   (6) Coupling agent TESPT (“Si69” from Evonik);    -   (7) Liquid diene polymer 1: non-functionalized liquid        polybutadiene (“POLYVEST 130” from EVONIK, number-average molar        mass (Mn): 4600 g/mol, Tg_(DSC)=−99° C., 1 mol % of 1,2-vinyl,        22 mol % of 1,4-trans, 77 mol % of 1,4-cis);    -   (8) Liquid diene polymer 2: hydroxyl-terminated liquid        polybutadiene produced by free radical polymerization (“POLYVEST        HT” from EVONIK, number-average molar mass (Mn): 2900 g/mol,        Tg_(DSC)=−80° C., 22 mol % of 1,2-vinyl, 58 mol % of 1,4-trans,        20 mol % of 1,4-cis, average functionality: 2.4 (that means that        a polybutadiene molecule has average 2.4 hydroxyl groups        irrespective its length)));    -   (9) Liquid diene polymer 3: triethoxysilane-terminated liquid        polybutadiene obtained by reacting hydroxyl-terminated        polybutadiene produced by free radical polymerization with        3-isocyanatopropyltriethoxysilane (“POLYVEST EP ST-E-100” from        EVONIK, number-average molar mass (Mn): 3300 g/mol,        Tg_(DSC)=−80° C., 22 mol % of 1,2-vinyl, 58 mol % of 1,4-trans,        20 mol % of 1,4-cis, average functionality: 2.5 (that means that        a polybutadiene molecule has an average 2.5 silane groups        irrespective its length));    -   (10) Oleic sunflower oil (“Agripure 80” from Cargill, Weight        percent oleic acid: 100%);    -   (11) Hydrocarbon resin C_(5/)C₉ type (“Escorez ECR-373” from        Exxon, Tg_(DSC)=44° C.);    -   (12) N-(1,3-dimethylbutyl)-N-phenyl-para-phenylenediamine        (“Santoflex 6-PPD” from Flexsys);    -   (13) Diphenylguanidine (“Perkacit DPG” from Flexsys);    -   (14) N-dicyclohexyl-2-benzothiazolesulphenamide (“Santocure CBS”        from Flexsys).

1.-20. (canceled)
 21. A rubber composition based on at least: anelastomer matrix comprising at least one first diene elastomer bearingat least one SiOR₁ function, R₁ being a hydrogen atom or a hydrocarbonradical, the SiOR₁ function not located at chain ends of the at leastone first diene elastomer; a reinforcing filler comprising a reinforcinginorganic filler; and a plasticizing agent comprising a liquidplasticizer comprising a liquid diene polymer bearing at least onefunction.
 22. The rubber composition according to claim 21, wherein theat least one first diene elastomer is a styrene-butadiene copolymer. 23.The rubber composition according to claim 21, wherein the at least onefirst diene elastomer further bears at least one amine function.
 24. Therubber composition according to claim 23, wherein the SiOR₁ functionbears the amine function.
 25. The rubber composition according to claim21, wherein R₁ of the SiOR₁ function is a hydrocarbon radical.
 26. Therubber composition according to claim 21, wherein the at least one firstdiene elastomer has a glass transition temperature of lower than −40° C.27. The rubber composition according to claim 21, wherein the elastomermatrix optionally comprises at least one second diene elastomerdifferent from the at least one first diene elastomer, wherein theamount of the at least one first diene elastomer is from 20 to 100 phr,and wherein the amount of the at least one second diene elastomer is 0to 80 phr.
 28. The rubber composition according to claim 21, wherein theamount of the reinforcing inorganic filler is more than 90 phr.
 29. Therubber composition according to claim 21, wherein the reinforcinginorganic filler predominately comprises silica.
 30. The rubbercomposition according to claim 21, wherein the reinforcing fillerfurther comprises carbon black, and wherein the amount of carbon blackis less than 10 phr.
 31. The rubber composition according to claim 21,wherein the amount of the liquid diene polymer is at most 25 phr. 32.The rubber composition according to claim 21, wherein the liquid dienepolymer has a glass transition temperature of less than −60° C.
 33. Therubber composition according to claim 21, wherein the liquid dienepolymer has a number average molar mass of less than 6000 g/mol.
 34. Therubber composition according to claim 21, wherein the liquid dienepolymer comprises 1,3-butadiene derived monomer units being 1,2-vinyl,1,4-trans and 1,4-cis, wherein a proportion of 1,2-vinyl in an entiretyof the 1,3-butadiene derived monomer units present in the liquid dienepolymer is less than 40 mol %, and wherein a sum of proportions of1,4-trans and 1,4-cis in the entirety of the 1,3-butadiene derivedmonomer units present in the liquid diene polymer is more than 60 mol %.35. The rubber composition according to claim 21, wherein the liquiddiene polymer is a liquid polybutadiene.
 36. The rubber compositionaccording to claim 21, wherein the liquid diene polymer is such that theSiOR₁ function comprises at least one function selected from the groupconsisting of silane functions, hydroxyl functions, anhydride functionsand combinations thereof.
 37. The rubber composition according to claim21, wherein the liquid diene polymer is such that the SiOR₁ function isa silane function.
 38. The rubber composition according to claim 21,wherein the liquid plasticizer further comprises a vegetable oil, andwherein the amount in phr of vegetable oil is higher than one-third ofthe amount in phr of the liquid diene polymer.
 39. The rubbercomposition according to claim 21, wherein the plasticizing agentfurther comprises a hydrocarbon resin, and wherein the amount in phr ofhydrocarbon resin is higher than that of the liquid diene polymer.
 40. Atire tread comprising a rubber composition according to claim 21.